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Ecological Exposure Research

Research in Action

Relative Risk of Pharmaceuticals in Waste Water

Functional Process Zones


There is potential for pharmaceutical drug residues to be present in treated municipal wastewater, however little is known about the extent of their prevalence in this environment or the potential risks they may pose.


EPA exposure scientists are conducting a survey of 50 of the largest U.S. municipal wastewater treatment plants. The plants chosen for the survey produce about 6 billion gallons a day of treated wastewater that is released into surface water such as rivers and streams. Together they treat over 15 percent of the treated wastewater produced in the United States every day.

EPA scientists are analyzing the wastewater effluent samples to determine the concentrations of 48 high-priority active pharmaceutical ingredients, steroid hormones, alkylphenolic compounds, bisphenol A, and perfluorinated chemicals.

Survey results will help EPA scientists test and refine a model they have developed for estimating concentrations of pharmaceuticals in wastewater. Currently, about 1,800 pharmaceuticals are approved for prescription use in the United States. The model could provide a means for estimating potential exposure rates to these pharmaceuticals, and provide scientists with information needed to estimate overall risks, and prioritize future research efforts on pharmaceuticals of greatest concern.

In developing the model, EPA scientists used pharmaceutical marketing data to help them prioritize the top 48 drugs to investigate. The pharmaceuticals that sold the greatest number of minimum daily dose equivalents per year in the United States were added to the list.

Results and Impact

Preliminary study results suggest that risks posed to healthy adult humans (and animals with similar physiology) by water-borne pharmaceutical residues is very low. EPA scientists want to look more closely at potential risks to sensitive human sub-populations, such as people with allergies, pregnant women, children, and people with impaired metabolisms. They also plan to study how water-borne pharmaceutical residue exposure may affect aquatic life.

Final study results should provide scientists with much more accurate estimates of the wastewater concentrations of 48 of the most used pharmaceuticals. And, if these measurements agree with their model predictions, the scientists should be able to use the model to estimate maximum individual and cumulative exposure rates in water for all pharmaceuticals used today.

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